FIGS. 25A and 25B are a schematic drawing and an overhead view explaining a light emitting diode assembly in the form of a light emitting device of the prior art having a light emitting diode as the light source thereof. In FIGS. 25A and 25B, a light emitting diode assembly 60 is composed of a printed wiring board 61, a submounting substrate 62 provided on the printed wiring board 61, a plastic hollow body 63 surrounding the periphery of the submounting substrate 62, a light emitting diode 65, and a transparent sealing resin 66 covering the light emitting diode 65.
The plastic hollow body 63 is integrally molded with a lead frame 64 by a thermosetting resin having an epoxy resin as a main component thereof. The printed wiring board 61 has printed wires 611 for the connection with a control circuit not illustrated for operating the light emitting diode 65 formed in a desired pattern by etching or the like. The submounting substrate 62 has a pair of wires 622 formed in the upper surface thereof by forming a vapor deposition pattern using etching or a mask.
In the plastic hollow body 63, the lead frame 64 passes through a sidewall. The plastic hollow body 63 is integrally produced by so-called insert or outsert molding (injection molding) in which a part of the lead frame 64 is embedded therein during molding. The plastic hollow body 63 reflects light emitted by the light emitting diode 65 with the surface of an inner wall thereof.
The light emitting diode 65 is provided with two electrodes 623 at the bottom, is cut out from a semiconductor wafer by dicing, and has the electrodes 623 connected to the wires 622 of the submounting substrate 62.
The transparent sealing resin 66 has heat resistance and is filled in the plastic hollow body 63 to form a flat or convex lens.
The light emitting diode package described in JP 2001-244508 A comprises two substrate portions insulated from each other, where a lower electrode of a vertical geometry light emitting diode is fixed to one substrate portion and an upper electrode of the vertical geometry light emitting diode is connected to the other substrate portion by a bonding wire.
In the surface-mounted light emitting device described in JP 2003-8074 A, flip chip light emitting diodes are fixed on substrate portions insulated from each other.
In the light emitting diode package described in JP 2005-19609 A, a flip chip light emitting diode is placed in a housing recess of a semiconductor substrate and the electrical connection to the light emitting diode is established by a wire.
Furthermore, in some conventional light emitting diode packages, a resin is inserted into an insulated part between electrically insulated metal cores. A production method of such a light emitting diode package is described, for example, in JP 2005-116579 A.
Also, in some conventional surface-mounted light emitting diodes, two divided metal core substrates are bonded together by an insulating adhesive and a submounting substrate is placed thereon. Such a surface-mounted light emitting diode is described, for example, in JP 2003-303999 A.
A flip chip light emitting diode of submounted type is advantageous in that by virtue of the absence of an electrode on the top thereof, the emitted light is entirely radiated to the outside.
On the other hand, as for a vertical geometry light emitting diode, development of those surpassing the flip chip emitting diode in terms of performance is proceeding. The vertical geometry light emitting diode allows a large current flow and enhanced illuminance, whereas the configuration of submounted type has a drawback that since heat generated from the diode can be hardly dissipated due to poor thermal conductivity, the package readily reaches a high temperature and this gives rise to occurrence of wiring disconnection or the like in the course of use. In addition, the submounted type also has a problem of poor productivity.
The vertical geometry light emitting diode now available becomes large-sized and assured of good emission efficiency and high illuminance. In a light emitting device using a vertical geometry light emitting diode, a wiring material, for example, a gold wire of 25 to 30 μm in diameter, is used for power supply to the light emitting diode, and the connection of the wiring material to the light emitting diode is performed by a thermosonic (ultrasonic thermocompression) method that is commonly used in wire bonding. However, the connection using this method has the following problems:
(1) the thickness of the wiring material used is limited and a large current cannot be passed or if a large current is passed, the material in the periphery burns out,
(2) fluctuation is produced in the bonding strength of the wiring material and separation of the wiring material readily occurs,
(3) the joining part is weak to vibrations and a sealing material is necessary for reinforcement, and
(4) cracking is readily produced in the electrode of the light emitting diode or in the semiconductor layer due to ultrasonic oscillation and pressure during the connection and therefore, the apparatus used needs to be subtly adjusted.
The light emitting diode is being used as a light emitting element in various uses and, for example, is used in a backlight device of a liquid crystal display panel. For example, the backlight device described in JP 2006-301209 A is a device for illuminating a color liquid crystal display panel from the back side, where a plurality of light emitting element rows each having a plurality of light emitting elements (light emitting diodes) disposed in a line are arrayed in parallel in the inside of the backlight housing so that the distance between the light emitting element at the end of the light emitting element row and the side plate of the backlight housing can differ between adjacent light emitting element rows.
With respect to a method for producing a light emitting device using a large amount of light emitting diodes as used in the backlight device of a liquid crystal display panel, predetermined members are fixed to predetermined sites of a lead frame, and the lead frame is then cut, whereby a light emitting device is produced. The production of such a light emitting device involves joining together of different members, for example, between a substrate and a light emitting diode, between an electrode of a light emitting diode and a lead wire, and between a reflector and a substrate. For optimizing the joining together of different members, it has been necessary to strictly control the temperature in the process of producing a light emitting device. If the temperature control is insufficient, this adversely affects the light emitting diode in many cases.